The present invention is in the field of multiple photoflash lamp arrays, such as flashcubes and planar arrays, adapted to be temporarily attached to a camera and capable of producing a plurality of flashes for taking a plurality of pictures. In general, these multilamp photoflash arrays or assemblies comprise a reflector unit having a plurality of adjacent reflector cavities, each having a photoflash lamp mounted therein and are well known in the art.
The conventional flashcube is one well known embodiment of such photoflash lamp arrays and an example of a flashcube is described in the U.S. Pat. No. 3,739,166 to R. M. Anderson. Various type linear or planar photoflash lamp arrays are also well known in the art wherein a series of reflectors are arranged in one or more rows which may face in the same direction to form a single-sided array or in opposite directions to form a two-sided array. An example of such two-sided array is described in the U.S. Pat. No. 3,598,984 whereas such single-sided array is described in the U.S. Pat. application entitled "Multiple Photoflash Lamp Unit" of K. H. Weber, Ser. No. 448,671, filed Oct. 22, 1973, now U.S. Pat. No. 3,937,946, and assigned to the assignee of the present invention.
As further illustrative of the various designs and constructions that have already been proposed for multiple lamp photoflash arrays, it is known to have associated flashlamp-reflector assemblies mounted adjacent to one another in one or more rows facing in the same direction and operatively associated by electrical circuit means so that a group of the flashlamps which are relatively further from the camera lens axis than are the other lamps of the unit will be flashed. This mode of operation can be accomplished with a lamp configuration in which the individual flashlamps are electrically connected to a printed circuitboard member with electrical contact being made to the camera by contact tabs located at opposite ends of the circuitboard which readily plug into a suitable receiving socket on the camera itself or on an adaptor therefor. An electrical energy source which may be contained within the camera is connected to said contact tabs so that a firing pulse produced by the source can be applied across said contacts depending upon the type of lamps used in the flashlamp array. If low voltage filament type flashlamps are employed in the array, the firing pulse source may be of the battery or battery-capacitor discharge type producing in synchronization with opening of the camera shutter, a pulse of approximately 3 volts to 15 volts or more and of sufficient energy to fire a single flashlamp. An example of a suitable low voltage flashlamp is disclosed in U.S. Pat. No. 3,506,385 to K. H. Weber and G. W. Cressman and an example of a low voltge flash-sequencing circuit is disclosed in the U.S. Pat. No. 3,532,931 to P. T. Cote and J. D. Harnden. If the flashlamps in the multiple flash array are of the so-called high voltage type, requiring a pulse of approximately of 1,000 - 2,000 volts, the firing pulse source may comprise a suitable battery-capacitor discharge and voltage step-up transformer type circuit, or may employ a compact piezolectric element arranged to be impacted or stressed in synchronization with opening of the camera shutter, so as to produce a firing pulse having a voltage of approximately 1,000 or 2,000 volts and of sufficient energy to fire a single flashlamp. An example of a high voltage flashlamp and a firing pulse source comprising a piezolectric element synchronized with a camera shutter is described in U.S. Pat. Nos. 2,972,937 and 3,106,080, both to C. G. Suits.
Radiation switches which are suitable in a flash-sequencing circuit of the type above generally described are also known. These switches which can be employed in various ways are converted from a high resistance or open circuit condition upon flashing of an adjacent flashlamp in the array to provide a low resistance circuit path to another unflashed lamp. A solid static switch which operates in this manner is described and claimed in U.S. patent application, Ser. No. 460,801, abandoned, filed Apr. 15, 1974, entitled "Switching Devices for Photoflash Unit," in the names of F. F. Holub et al, and assigned to the assignee of the present invention. The described switch material composition comprises a mixture including a carbon-containing silver salt and an organic polymer binder exhibiting improved shelf life under conditions of high relative humidity especially at above normal ambient temperatures. Various modifications of such switch material composition are disclosed to include a mixture of silver oxide with a carbon-containing silver salt as the silver source which is converted to elemental silver upon lamp flashing along with incorporation of various additives to improve the desired performance. One disclosed type of additive is a radiation absorptive filler such as carbon if the silver source itself does not absorb sufficient impinging actinic radiation from the flashlamp reliably to provide a low ohmic conversion.